One weekend when I was a student in Hungary, a group of friends invited me on an excursion. They regularly hiked in the Tatra Mountains in neighboring Slovakia, up to a (cheap) chateau. It was maybe a three-hour drive, one they were used to. I should have been more wary; they were all athletes and this hike was a serious endeavor.
But the trip hit an early snafu when we got to the border. My friends were all Hungarian citizens, and I wasn’t — and the border crossing they routinely used for these trips was only for locals, for Hungarian and Slovak citizens. There were border crossings elsewhere for other international citizens. We were standing on a rural road with no human-made structures except the guard houses and the road, pleading (unsuccessfully) with the border guards. There was a simple painted white line across the road, and I could not cross it. As absurd as it sounds, that painted white line was, for me, an insurmountable geopolitical barrier.
